hundreds of thousands of them. 它们的数量无以为计

76. This hundred metre high mound is made entirely of bat droppings -
    这堆100多米高的东西 全都是蝙蝠的排泄物
77. guano.
    粪便
78. Its surface is covered by a thick carpet of cockroaches,
    地面上爬满了密密麻麻的蟑螂
79. hundreds of thousands of them.
    它们的数量无以为计
80. Caves are one of the few habitats on Earth not directly powered by sunlight.
    洞穴是地球上少数几种 不直接依赖阳光的生态环境之一
81. In the absence of plants this food chain is based on a continuous supply of bat droppings.
    在缺少植物的情况下 这里的食物链 完全依赖供应不断的蝙蝠粪便
82. The cockroaches feed on the guano
    蟑螂的食物就是粪便

来自《行星地球 第一季 第四集 Planet Earth S01E04 洞穴》第 79 行